The present invention relates to electric heaters. More particularly, this invention relates to clips and insulators for use in structures that support heating elements or coils in electric heaters, such as open coil heaters.
Open coil heaters typically include structures that support heating elements in a stacked or spaced parallel relationship with respect to other coils in the heater. The heating elements are operably connected to a terminal box assembly including control circuitry that selectively energizes the heating elements. Often, separate support structures are used to individually position each heating element within the heater. Alternatively, complex support structures have been designed that can support multiple coils within the heater.
Open coil heaters are known in the art. Reference is made, for example, to U.S. Pat. No. 4,144,445 (Thweatt, Jr.); U.S. Pat. No. 5,578,232 (Engelke); U.S. Pat. No. 5,093,558 (Blystone et al.); and U.S. Pat. No. 4,692,599 (Howard et al.). Open coil heaters typically include structures that support heating elements in a stacked or spaced parallel relationship with respect to other coils in the heater. The heating elements are operably connected to a terminal box assembly including control circuitry that selectively energizes the heating elements.
In the electric heater industry, the use of structural members or clips that partially encircle insulators and are, in turn, supported by being welded to frame bars is well known. An example is shown in U.S. Pat. No. 4,692,599 to Howard et al. (xe2x80x9cthe Howard patentxe2x80x9d). One disadvantage to such a construction is the amount of welding required to attach each clip or support member to the frame bar, and that the welding is difficult to automate.
Other heater designs used in the industry reduce the amount of welding but at the expense of flexibility in design and at other costs. Reference is made, e.g., to U.S. Pat. No. 5,954,983 (Holmes) and U.S. Pat. No. 4,472,624 (Janning).
U.S. Pat. No. 5,954,983 to Holmes discloses an embodiment that eliminates welding of the member supporting the insulator onto the frame by making the frame and the clip from one piece of metal. One disadvantage to this design, however, is that once a particular number and spacing of clip members along a frame is chosen and produced, changing that configuration (such as by moving the clip members closer together) is difficult and costly.
U.S. Pat. No. 4,472,624 to Janning discloses an embodiment wherein insulators are held in the frame by placing them into roughly circular holes cut into cross beams, which in turn are welded on each end to a frame. Several insulator-supporting holes are cut into each cross beam. The welding is easier and less costly than that in the Howard patent because the welding in Janning is performed toward the outside of the frame, farther away from the insulators. There may also be fewer welds per insulator, depending on the number of insulators supported in each cross beam. On the other hand, changing the configuration (such as the spacing or number of insulators on each cross beam) in Janning is more difficult and costly than in the Howard patent, and significant scrap metal is produced from cutting or punching holes in the cross beams.
Accordingly, a primary object of this invention is to eliminate welding of clips onto the frame bar, while maintaining the flexibility of design permitted by the Howard patent.
A further object is to provide a procedure that, in addition to being more flexible than welding, is also cheaper and easier than welding.
Another object of this invention is to provide for a connection that is very strong.
These and other objects are achieved in the present invention.
One aspect of the present invention provides a clip for connecting one or two insulators to a rail of an electric heater frame. Broadly, the clip of this invention is composed of:
a main body;
means for securing at least one insulator to the main body, and
at least one bendable metal clinching member extending from the main body, wherein the clip is securable to the rail by bending the clinching member around the rail.
A novel feature of this invention is that welding is not required to secure the clip to a rail. Specifically, the particular clinching member(s) present in the clip allows the clip to be secured to the rail without welding.
A second aspect of the present invention is directed to a rail/clip assembly composed of a rail and at least one clip of this invention secured to the rail. The rail preferably has a T-shaped cross-section and contains a ridge portion and a stem portion. The clip is secured to such T-shaped rail by bending the clinching member of the clip around the ridge portion of the rail.
A third aspect of the present invention is directed to an insulator which is intended to be secured to a rail via the clip of this invention. The insulator of this invention is composed of:
upper and lower longitudinal sides, each longitudinal side having a central groove and two side notches formed therein, the central groove being disposed between the side notches;
first and second transverse sides, each transverse side having an end groove formed therein; and
front and back faces, each face having a transverse midsection disposed between the central grooves and being coaxial with a symmetrical transverse axis of the face; each face further having a longitudinal midsection disposed between the end grooves and being coaxial with a symmetrical longitudinal axis of the face.
A fourth embodiment of the present invention is directed to a rail/clip/insulator assembly, composed of a rail, the clip of this invention, and an insulator (preferably the insulator of this invention), wherein the insulator is secured to the rail via the clip. Specifically, the insulator is attached to the clip means for securing an insulator to the main body.
A fifth embodiment of the present invention is directed to an electric heater which uses clips within the scope of this invention to secure insulators to at least one rail of the heater. The heater of this invention is composed of:
a terminal plate;
a cross-beam;
at least one rail, the rail being attached (preferably butt-welded) at one end to the terminal plate and attached at an opposite end to the cross-beam;
at least one clip secured to the at least one rail, the clip containing:
a main body;
a means for securing an insulator to the main body, and
at least one bendable metal clinching member extending from the main body, wherein the clinching member is bent around the rail so as to secure the clip to the rail; and
an insulator attached to the means for securing an insulator to the main body.
A sixth embodiment of the present invention is directed to a method of securing an insulator to a rail, involving the steps of:
(1) providing a rail, an insulator and a clip, wherein the clip contains a main body, a means for securing an insulator to the main body, and at least one bendable metal clinching member extending from the main body,
(2) securing the clip to the rail by bending the bendable clinching member around the rail; and
(3) securing the insulator to the means for securing an insulator to the main body, wherein step (3) may be performed before or after step (2).
A seventh aspect of the present invention is directed to a method for making an electric heater, involving the steps of:
(1) providing a terminal plate, a cross-beam, at least one rail, at least one clip and at least one insulator, wherein the clip comprises a main body, a means for securing an insulator to said main body, and at least one bendable metal clinching member extending from the main body,
(2) attaching a first end of the rail to the cross-beam and a second end of the rail to the terminal plate;
(3) securing the clip to the rail by bending said bendable clinching member around said rail; and
(4) securing the insulator to the clip means for securing an insulator to the main body, wherein steps (2)-(4) may be performed in any order.
In the present invention, rather than welding clips onto the frame bar, clinch clips are used which are clinched or crimped onto a rail, preferably a T-shaped rail. No welding is required to attach the clips to the rail. The clinching procedure is easier, cheaper and more flexible than welding, and also provides a connection that is very strong.